1. Field of the Invention
The present disclosure relates generally to an interference cancellation scheme in a communication system, and more particularly, to an interference cancellation scheme using a universal constellation diagram in a User Equipment (UE).
2. Description of the Related Art
To improve coverage and spectral efficiency, a next-generation wireless communication system has been designed, which operates as a base station having an aggressive frequency reuse factor and a high density. In particular, the base station may apply (or employ) multiple access technologies to allow multiple UEs to share the same time-frequency resources. The multiple access technologies may include, for example, Spatial Division Multiple Access (SDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and the like.
A UE may suffer capacity loss due to inter-cell interference or intra-cell interference. Specifically, while the UE may receive the desired signals from a serving cell, it may also receive undesired signals from the serving cell or an interfering cell. In order to improve cell-edge performance in interference-constrained scenarios, advanced technologies such as, for example, Coordinated MutiPoint (CoMP) transmission and enhanced Inter-Cell Interference Coordination (eICIC), have recently been embodied in the Long Term Evolution (LTE) standard.
Advanced interference cancellation technology, which is referred to as Network-Assisted Interference Cancellation and Suppression (NAICS), has been studied by the 3rd Generation Partnership Project (3GPP). Advanced interference aware signal detection has attracted attention during a recent study of the LTE-Advanced (LTE-A) system.
For example, a UE may cancel or remove interference signals from received signals. To this end, the UE may utilize interference information including a constellation diagram used for the interference signals. A point on the constellation diagram is called a constellation point, and a possible symbol that can be selected in a given modulation scheme may be expressed as a point on the complex plane.
The UE may know (or be aware of) an interference constellation diagram by receiving transmission parameters associated with the interference modulation scheme and order (or level) by blind detection, without the help of the network, or by signaling, with the help of the network. Specifically, a UE may perform interference cancellation through detection or network signaling, assuming that the UE has good knowledge of transmission parameters such as, for example, a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a modulation level.
These interference parameters may vary depending on a frequency unit of one Resource Block (RB) and a time unit of one time unit (e.g., Transmission Time Interval (TTI) or slot). Thus, signaling of the RB and the time unit (e.g., TTI or slot) is required. However, it is difficult for a serving cell to dynamically signal the transmission parameters, such as the modulation scheme and the order, in units of, for example, slots or RBs.
Further, the dynamic signaling may cause a very large overhead. However, if the signaling is excluded or omitted, performance degradation and computational cost may be significant.